3 - North Washinton Avenue Discussion

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3113/13 Curb Extensions(Bulb-outs)I SF Better Streets a i u Teet for me nearest auto travel lane a 11 to 12 feet for the nearest travel lane if it is a transit lane ■ 12 feet for the nearest travel lane If it is a designated freight route or industrial street a 5 feet or the full width of any adjacent bicycle lanes Typical Bulb-Out Dimensions j Before reducing the width of the proposed bulb-out,consider modifications to lane striping across the entire roadway to provide for the above-listed clearances.Since bulb-outs are often expensive to construct,they should be sufficiently wide to maximize their benefit.Bulb-outs less than 4 feet in width may not be a cost- effective solution as compared to other potential interventions. Curb extensions should not encroach on cyclists'space. Where bike lanes use a painted inside edge,the bike lane should be painted continuously as the bike lane passes the curb extension,and the bulb-out should be set bade so that the gutter does not extend into the bike lane.On lower # speed and volume streets where bikes can travel in mixed ?` flow with vehicles,wider curb extensions may be appropriate,but care should be taken not to force cyclists $ to merge unexpectedly with faster moving cars at the end where bike lanes a,apre en,, ur�,x,dn,;ons shnutd an obnck»n of the block.If bulb-outs extend beyond the limit of parked th,tthe guuerpan day —t—t ndinmihn 6fke tone cars,additional efforts should be made to ensure their visibility. Bulb-outs should continue at least to the inside edge of the crosswalk,and ideally extend 5 feet beyond the property line before beginning to return to the curb to provide additional width for pedestrians,landscaping,or other streetscape features.Existing driveways may cross through bulb-outs. Radii Curb extensions should follow all curb radius guidelines.Where turn radii make adding bulb-outs at each corner prohibitive,strive for two bulbs per intersection,kitty-corner to each other,in order to improve pedestrian conditions for all four crossings of an intersection. Curb extensions should return to the prevailing curb line as sharply as possible to maximize useable space and minimize parking loss,per the following guidelines: Standard return:Standard bulb-outs should be designed with an inner/outer curb radius of 20'and 10',sometimes reduced to 15'and 10',to enable street sweeping Machinery to sweep the entire curbiine. Non-standard return:Sharper curb returns increase pedestrian space and minimize parking loss while better LMMdat►*patn defining a curb extension.However,they are more difficult costly to maintain.Where maintenance funding or agreements are in place to account for this,designs may Consider the non-standard treatments described below: ■ 80 degree return:Curb extensions may return to the *0441isatttd#*then prevailing curb line at a 90 degree angle.This configuration may be used with parallel or perpendicular parking. t ■ 45 degree return:Curb extensions may return to the prevailing curb line at an angle.his may be used with either parallel parking(45 degree return)or angled parking(at angle of parking lane). wwwsfbetterstareets.org/find-project-types/pedestriari-safetyard-traffic-cairring/traffic-calving-okeNevicurb-extensiorts/ 315